I absolutely think it's worth playing, but you could build a whole deck out of cards I've played in EDH that are worse than
compost so I may not be the best judge.
I personally don't play it simply because in my playgroup I'm the only one that really plays black. Each of the other people in my group have exactly one deck with black in (and only as a supporting colour) so it's definitely not worth it for me. Play it against me though and you're likely to draw half your deck.
I'm personally never too concerned with running and amount of "dead" cards anyway if they have high ceilings. Even if the match up is bad and the card isn't going to do much, it's nice to have something that you can discard to
faithless looting or pitch to
Endurance or whatever. Even dead cards can offer additional utility in other aspects of the game.
For the record, I'm not advocating putting cards into your deck specifically because you won't be sad if you discard them, but if they have a high ceiling like
compost does, it's worth the
gamble in my opinion.